Electromagnetically driven valve and driving method of the same

ABSTRACT

An electromagnetically driven valve includes a valve element that has a valve stem and moves in reciprocating motion in a direction in which the valve stem extends; a disc that is interlocked with the valve element at a driving end, extending to a pivoting end, from which a central axis extends and around which the disc oscillates; a coil that oscillates the disc; a power supply that supplies electric current to the coil; and an ECU that controls the flow of current from the power supply to the coil. During the initial period of operation of the disc, the ECU controls the current so that it is supplied from the power supply to the coil in cycles, and in accordance with the voltage and temperature, controls the number of current cycles, the cycle length, and the value of the current.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2005-229605 filed onAug. 8, 2005 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to an electromagnetically driven valve,and more particularly, relates to a pivot-type electromagneticallydriven valve that is used for an internal combustion engine and drivenby electromagnetic force and elastic force and to a means of driving thesame.

2. Description of the Related Art

An electromagnetically driven valve has been disclosed, for example, inthe U.S. Pat. No. 6,467,441.

The electromagnetically driven valve has a problem in that its slidingresistance at low temperature is different from that at hightemperature, so that its controllability also varies. Moreover, whenvariable lift control is used to hold a disc out of contact with a core,if coil current fluctuates due to load-induced fluctuations in batteryvoltage, it is impossible to control the holding of theelectromagnetically driven valve in a stable manner.

SUMMARY OF THE INVENTION

The invention aims to provide an electromagnetically driven valve thatcan be driven in a stable manner.

A first aspect of the invention relates to an electromagnetically drivenvalve that is operated by a combined action of electromagnetic force andelastic force. The electromagnetically driven valve includes a valveelement that has a valve stem and moves in reciprocating motion in adirection in which the valve stem extends; an oscillating member that isinterlocked with the valve element at an driving end, extending to apivoting end, from which a central axis extends and the oscillatingmember oscillates around the central axis; a coil that oscillates theoscillating member; a power supply that supplies electric current to thecoil; and a control portion that controls the flow of electric currentfrom the power supply to the coil. During the initial period ofoperation of the oscillating member, the control portion controls theflow of electric current so that electric current is provided from thepower supply to the coil in cycles. Specifically, during the initialperiod of operation, the control portion controls the number of cycles,the cycle length, and the value of the electric current in accordancewith the voltage and temperature.

In an electromagnetically driven valve configured in the above-describedmanner, a control portion controls the periodic number, the periodiclength and the current value in accordance with the voltage andtemperature, at the initial drive; therefore it can accelerate heatingto improve controllability by applying higher electric current at thelow temperature period when sliding resistance is large.

A second aspect of the invention relates to an electromagneticallydriven valve that is operated by a combined action of electromagneticforce and elastic force. The electromagnetically driven valve includes avalve element that has a valve stem and moves in reciprocating motion ina direction in which the valve stem extends; an oscillating member thatis interlocked with the valve element at a driving end, extending to apivoting end, from which a central axis extends and the oscillatingmember oscillates around the central axis; a core of an electromagnetthat oscillates the oscillating member; and a permanent magnet that islocated on the outer side of the driving end of the oscillating memberand is positioned in such a way that a magnetic flux passing through theoscillating member and the core becomes greater.

In the electromagnetically driven valve configured as described above,the magnetic flux passing through the oscillating member and the corebecomes greater, thereby reducing electric power consumption and makingthe valve less subject to the effects of voltage when the valve is heldat an intermediate lift position. As a result, an electromagneticallydriven valve is provided that improves controllability and ensuresstable operation.

According to the invention, an electromagnetically driven valve isprovided that ensures stable operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of theinvention will become apparent from the following description ofpreferred embodiments with reference to the accompanying drawings,wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a cross-sectional view of an electromagnetically driven valvein accordance with a first embodiment of the invention;

FIG. 2 is a schematic circuit diagram of the electromagnetic valve shownin FIG. 1;

FIG. 3 is a graph that shows the relation between electric current andvalve lift during the initial period of operation;

FIG. 4 is a cross-sectional view of an electromagnetically driven valvethat shows a neutral position;

FIG. 5 is a cross-sectional view of an electromagnetically driven valvethat shows a closed-valve state;

FIG. 6 is a map of electric current values in relation to differenttemperatures and voltages;

FIG. 7 is a map of cycle lengths in relation to different temperaturesand voltages;

FIG. 8 is a map of the number of cycles in relation to differenttemperatures and voltages;

FIG. 9 is a cross-sectional view of an electromagnetically driven valvein accordance with a second embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be explained below with reference tothe drawings. Note that in the embodiments below, identical referencesymbols are used to represent identical or equivalent elements, andexplanations thereof are not repeated.

(First Embodiment)

FIG. 1 is a cross-sectional view of an electromagnetically driven valvein accordance with an embodiment of the invention. Anelectromagnetically driven valve 1 operates by the combined action ofelectromagnetic force and elastic force. The electromagnetically drivenvalve 1 includes a valve element 14 that has a valve stem 12 serving asa valve shaft and moves in reciprocal motion in the direction in whichthe valve stem 12 extends (arrow 10); a disc 30 serving as anoscillating member that is interlocked with the valve element 14 atdriving end 32 and that oscillates around an axis 35, located atpivoting end 33; coils 62 and 162 that drive an upper electromagnet 60and a lower electromagnet 160 that oscillate the disc 30; a power supply200 that supplies electric current to the coils 62 and 162; and anelectronic control unit (ECU) 100 serving as a control portion thatcontrols the flow of electric current from the power supply 200 to thecoils 62 and 162. During the initial period of operation of the disc 30,the ECU 100 controls the flow of electric current so that electriccurrent is supplied from the power supply 200 to the coils 62 and 162 incycles. Specifically, the ECU 100 controls the number of current cycles,the cycle length, and the current value during the initial period ofoperation in accordance with the voltage and temperature.

A U-shaped housing 51 is a base member, and various elements areinstalled in the housing 51. The upper electromagnet 60 and the lowerelectromagnet 160 respectively include cores 61 and 161, which are madeof magnetic material, and the coils 62 and 162, which are wound aroundthe cores 61 and 161. The flow of electric current to the coils 62 and162 generates a magnetic field, which drives the disc 30. The disc 30 isarranged between the upper electromagnet 60 and the lower electromagnet160, and the disc is attracted to either of them by the attraction forceof the upper electromagnet 60 and the lower electromagnet 160. Thiscauses the disc 30 to move in reciprocal motion between the upperelectromagnet 60 and the lower electromagnet 160. The reciprocal motionof the disc 30 is transmitted to a stem 46 through a long hole 22 and apin 21.

The electromagnetically driven valve 1 in the embodiment constitutes oneof an intake valve or exhaust valve in an internal combustion enginesuch as a gasoline engine and diesel engine. The embodiment sectiondescribes the case where a valve element serves as an intake valvefitted to an intake port 18, however the invention is applicable to avalve element that serves as an exhaust valve.

FIG. 1 shows the pivot-type electromagnetically driven valve 1. The disc30 is used as a driving mechanism. The housing 51 is installed on acylinder head 41; and the lower electromagnet 160 is arranged on theside closer to the cylinder head 41, while the upper electromagnet 60 isarranged on the side farther from the cylinder head 41. The coil 62,which configures the upper electromagnet 60, and the coil 162, whichconfigures the lower electromagnet 160, are connected by a wire 202.Moreover, the coil 62 is connected to the power supply 200 by a wire201, and the coil 162 is connected to the power supply 200 by a wire203. In other words, the coils 62 and 162 are connected in series to thepower supply 200.

The disc 30 includes an arm portion 31 and a bearing portion 38, and thearm portion 31 extends from driving end 32 to pivoting end 33. The armportion 31 is a member that is attracted by the upper electromagnet 60and the lower electromagnet 160; so that it oscillates (or pivots) inthe direction indicated by the arrow 30a. The bearing portion 38 is setat an end of the arm portion 31, and the arm portion 31 pivots aroundthe bearing portion 38. It is possible for the upper surface of the armportion 31 to come into contact with the upper electromagnet 60, and itis possible for the lower surface of the arm portion 31 to come intocontact with the lower electromagnet 160.

The bearing portion 38 is cylindrical, and a torsion bar 36 isaccommodated therein. A first end of the torsion bar 36 is fitted intothe housing 51 by means of a spline fitting, while the other end isfitted into the bearing portion 38 of the disk 30. Consequently, whenthe bearing portion 38 pivots, a force in the opposite direction to therotation is transmitted from the torsion bar 36 to the bearing portion38. Thus a reaction force is constantly applied to the bearing portion38 in a neutral direction. At driving end 32 of the disk 30, the stem 46is provided in such a way that force is imparted to it from the disc 30,and the stem 46 is guided by a stem guide 45. The stem 46 and the disc30 can oscillate in the direction indicated by the arrow 30a.

The housing 51 has a projection 52, and pivoting end 33 of the disk 30is accommodated therein. A bearing 59 is arranged between the bearingportion 38 and the projection 52 of the housing 51.

The intake port 18 is provided in the lower part of the cylinder head41. The intake port 18 is a passage for the introduction of intake airinto a combustion chamber, and either air-fuel mixture or air passesthrough the intake port 18. A valve seat 42 is provided between theintake port 18 and the combustion chamber, thereby improving thesealability of the valve element 14.

The valve element 14 is installed on the cylinder head 41 as an intakevalve. The valve element 14 includes the valve stem 12 extending in thelongitudinal direction and a bell portion 13 attached at the end of thevalve stem 12. The valve stem 12 is guided by a stem guide 43 and isfitted with a spring retainer 19. The spring retainer 19 is energized inthe upward direction by a valve spring 17. Thus both the spring retainer19 and the valve stem 12 are energized by the valve spring 17.

The ECU 100 controls electric current flowing from the power supply 200to the coils 62 and 162. The ECU 100 obtains temperature and voltagedata from a temperature sensor 102 and a voltage sensor 101. The voltagesensor 101 monitors voltage from the power supply 200. The temperaturesensor 102 detects temperature (water temperature, air temperature, orthe temperature of the electromagnetically driven valve 1). The ECU 100is connected to a memory unit 104, in which various map data are stored,including the current cycles and the current values that flows into thecoils 62 and 162.

FIG. 2 is a schematic circuit diagram of the electromagnetically drivenvalve shown in FIG. 1. As FIG. 2 shows, the two coils 62 and 162 areconnected in series to the power supply 200. This embodiment describesan example where the two electromagnets 60 and 160 are arranged on theupper and lower sides respectively, but this example is non-limiting,and more electromagnets may be provided.

FIG. 3 is a graph that indicates the relationship between the valve liftand electric current during the initial period of operation. FIG. 4 is across-sectional view of the electromagnetically driven valve indicatingthe neutral position. FIG. 5 is a cross-sectional view of theelectromagnetically driven valve showing a closed-valve state. Withreference to FIG. 1 to FIG. 5, motion mechanism of theelectromagnetically driven valve is described. In the neutral state, thearm portion 31 on the disc 30 is positioned on the center of the upperelectromagnet 60 and the lower electromagnet 160, as shown in FIG. 4.This condition continues until a time t10, at which point a electriccurrent I flows to the coils 62 and 162 until a time t11. Because thedistance between the arm portion 31 and the upper electromagnet 60 ismade slightly shorter than that between the arm portion 31 and the lowerelectromagnet 160, a large force acts between the arm portion 31 and theupper electromagnet 60, so that at time t11, the valve element 14 movesfrom the neutral position toward the closed-valve position.

At time t11 the electric current is reduced. Once the arm portion 31moves upward, downward torsion force is applied to it by the torsion bar36. As a result, the arm portion 31 moves downward until moves below theneutral position, at which time it stops and then starts to move upward.When it starts moving upward, electric current once more flows to thecoils 62 and 162, and the arm portion 31 is strongly drawn upward. Thisreciprocating motion is repeated from cycle 1 to cycle 3. Through thisprocess, the amplitude of the movements of the valve element 14gradually becomes greater until the valve element 14 is finally in theclosed state. The electric current cycles (cycle 1 to cycle 3 in FIG. 3)are controlled during this initial period of operation.

Once the valve-closed state shown in FIG. 5 is attained, the arm portion31 can be held by the upper electromagnet 60 as long as a small holdingelectric current is supplied to the coil 62.

The cycles shown in FIG. 3 are varied according to the voltage andtemperature. FIG. 6 shows a map of current values in relation todifferent temperatures and voltages. FIG. 7 shows a map of cycle lengthsin relation to different temperatures and voltages. FIG. 8 shows a mapof the number of cycles in relation to different temperatures andvoltages. At first, temperature and voltage are measured by thetemperature sensor 102 and the voltage sensor 101 shown in FIG. 1. Basedon the measured temperature and voltage, the ECU 100 calculates anappropriate current value for the initial period of operation, using theFIG. 6 current map stored in the memory unit 104. For example, if thetemperature stays between T2 and T3 and the voltage is between V3 andV4, the electric current for the initial period of operation will becalculated from the four current values I23, I33, I24, and I34 on theelectric current map. The ECU 100 calculates the length of each cyclebased on the FIG. 7 cycle length map. Under the above-mentionedtemperature and voltage conditions, the ECU 100 calculates the cyclelength based on the cycle lengths L23, L33, L24, and L34 on the cyclelength map.

The ECU 100 also calculates the number of cycles based on the FIG. 8 mapof the number of cycles. Under the above-mentioned temperature andvoltage conditions, the ECU 100 calculates the number of cycles based onthe numbers of cycles N23, N33, N24, and N34 on the map. The map datashown in the FIG. 6 through FIG. 8 are stored in the memory unit 104,and the ECU 100 can always access the memory unit 104.

That is, in the embodiment of the invention, the electric current, cyclelength, and number of cycles for the initial period of operation aremapped according to the temperature and voltage, and are then controlledto conform to the map based on monitoring values that are input from thetemperature and voltage sensors. Particularly, when the temperature isvery low and the sliding resistance is high, the normal set value forover-current is momentarily increased. When the temperature is very low,the difference between the measured temperature and the heat-resistancelimit temperature of the coils 62 and 162 is greater than under normaloperating conditions. The amount by which the electric current isincreased is therefore set so that the amount of temperature increase inthe coils, due to their heating by the increased electric current, willbe equal to the increased temperature difference between the measuredtemperature and the heat-resistance limit temperature of the coils 62and 162. The number of cycles for the initial period of operation whenthe temperature is very low is set so that the temperature of anactuator rises enough to lower the high sliding resistance almost to thesliding resistance level under normal operating conditions. That is, theflow of electric current is controlled so that the upper and lowerelectromagnets 60 and 160 are heated. In an electromagnetically drivenvalve configured in this manner, the controllability of theelectromagnetically driven valve 1 can be improved by accelerating itsheating when the temperature is low and the sliding resistance is high.

(Second Embodiment)

FIG. 9 is a cross-sectional view of an electromagnetically driven valvein accordance with a second embodiment of the invention. In theelectromagnetically driven valve in accordance with the secondembodiment of the invention, a permanent magnet 300 is provided on theouter side of driving end 32 of an arm portion 31. The permanent magnet300 is positioned so that it is apart from a core 161. As a result ofthis arrangement, the arm portion 31 is held in a position where it isnot in direct contact with the core 161. An electromagnetically drivenvalve 1 in accordance with the second embodiment of the invention is anelectromagnetically driven valve that is operated by the combined actionof electromagnetic force and elastic force. The electromagneticallydriven valve 1 includes a valve element 14 that has a valve stem 12 andmoves in reciprocal motion in the direction in which the valve stem 12extends; a disc 30 that is interlocked with the valve element 14 atdriving end 32 and that oscillates around an axis 35, located atpivoting end 33; a core 161 of an lower electromagnet 160 thatoscillates the disc 30; a permanent magnet 300 arranged on the outerside of the disc 30 and positioned in such a way that a magnetic fluxthat passes through the disc 30 and the core 161 in a directionindicated by arrow 301 becomes greater. In the embodiment the amount oflift of the valve element 14 is made variable, and the permanent magnet300 is arranged on the outer side of the disc 30 in order to reduceelectric current (power consumption) when holding the disc 30 out ofcontact with the core 161. The permanent magnet 300 is positioned apartfrom the core 161 and close to driving end 32, yet not in direct contactwith an arm portion 31. The arrangement of the permanent magnet 300 inthis way increases the flow of the magnetic flux generated by thepermanent magnet as indicated by the arrow 301. As a result, powerconsumption can be reduced and the valve can be made less subject to theeffects of voltage when the arm portion 31 is held at the intermediatelift position, so that a highly controllable electromagnetically drivenvalve 1 is provided.

The first and second embodiments of the invention have been explainedabove, but numerous variations of the embodiments shown here arepossible. The electromagnetically driven valve is not limited to thesingle-disc driven type, and it may be structured so that anelectromagnet is arranged between two parallel disks.

The embodiments disclosed herein are illustrative examples in everyrespect and should be considered to be non-limiting. The scope of theinvention is indicated not by the explanations above, but by the scopeof the claims, and it is intended that the equivalents of the claims andall modifications within the spirit and scope of the claims be included.

The invention can be used, for example, in the field ofelectromagnetically driven valves for internal combustion engines thatare mounted in vehicles.

1. An electromagnetically driven valve that is operated by the combinedaction of electromagnetic force and elastic force, comprising: a valveelement that has a valve stem and moves in reciprocating motion in adirection in which the valve stem extends; an oscillating member that isinterlocked with the valve element at a driving end, extending to apivoting end, from which a central axis extends, and the oscillatingmember oscillates around the central axis; a coil that oscillates theoscillating member; a power supply that supplies electric current to thecoil; and a control portion that during the initial period of operationcontrols at least one of a number of cycles, a cycle length, and a valueof an electric current provided in cycles to the coil in accordance withthe voltage of the power supply that drives the electromagneticallydriven valve and temperature.
 2. An electromagnetically driven valveaccording to claim 1, wherein, as the temperature decreases, the controlportion increases the value of the electric current that is provided tothe coil in cycles during the initial period of operation.
 3. Anelectromagnetically driven valve according to claim 1, wherein, as thetemperature decreases, the control portion increases the number ofcycles in which electric current is provided to the coil during theinitial period of operation.
 4. The electromagnetically driven valveaccording to claim 1, wherein the coil includes an upper coil and alower coil, and the oscillating member is provided between the uppercoil and the lower coil.
 5. An electromagnetically driven valve that isoperated by the combined action of electromagnetic force and elasticforce, comprising: a valve element that has a valve stem and moves inreciprocating motion in a direction in which the valve stem extends; anoscillating member that is interlocked with the valve element at adriving end, extending to a pivoting end, from which a central axisextends, and the oscillating member oscillates around the central axis;a core of an electromagnet that oscillates the oscillating member, and apermanent magnet that is located on the outer side of the oscillatingmember and arranged in such a position that magnetic flux passingthrough the oscillating member and the core becomes greater.
 6. Theelectromagnetically driven valve according to claim 5, wherein the coreof the electromagnet includes an upper coil and a lower coil, and theoscillating member is provided between the upper coil and the lowercoil.
 7. A method of driving an electromagnetically driven valve that isoperated by the combined action of electromagnetic force and elasticforce comprising: measuring a voltage of a power supply that drives theelectromagnetically driven valve and a temperature; and controlling atleast one of a number of electric current cycles, a cycle length, and avalue of electric current provided in cycles to a coil in accordancewith the measured voltage and temperature, during the initial period ofoperation of an oscillating member.